This invention relates to a device for sorting and sizing produce. A wide variety of machines have been used to size produce such as a screen conveyor constructed with holes of a designated diameter to allow the undersized produce to fall through. The problems are the screen has a short life as the holes stretch, wear rapidly, require a shaking and bouncing to dislodge the larger produce from occupying the available holes necessary for separation. Elongated produce will not rotate to fall through if not bounced and shaken.
Several attempts have been made to remedy the situation. The Milestone (U.S. Pat. No. 3,721,345) screw sizer uses lateral rotating screws that have the ridges substantially aligned. The produce considered too small are supposed to fall through the open holes, as the potatoes travel or are conveyed across the deck of rotating screws.
A major problem with this arrangement is that the deck is not large enough to separate the small potatoes and to allow them time to find an unoccupied hole to fall through. The screw action shown in the patent drawing needs just seven rotations to convey from start to end. The individual screws, which all rotate sideways, tend to move the potatoes to the side. This action does not separate, but bunches the potatoes to the side to flow off the deck in mass, not separated. Each screw has a long opening the length of the screw, thus the opening is not round and cannot adhere to a specific size such as a 2 inch diameter. The screws are supported with a bearing at both ends, and not cantilevered. The length of travel across the bed, while maintaining a space between the screws, cannot be increased substantially.
The rotation energy of motion of the screw is not concentrated towards the opening, but directional, as evident by the movement toward two different right angle paths. This disrupts the rotation movement necessary to align oblong potatoes to a vertical position directly on an open hole.
A traveling expanding roll sizer has rollers which expand the space between the rollers as they travel over a takeaway belt. This allows for the larger diameter produce to travel further. The problem is oval shaped produce has narrow ends and a considerably wider cross section, thus for example a round fat potato is carried farther than a long thin potato, but with a weight of much less.
A stationary spool sizer is a series of stationary shafts providing spools with rotational motion, but no forward motion. The problems here are that the holes acquire produce that is discharged neither by passing over nor falling through, thus the plugged holes soon limit the separation ability and many undersigned pieces carry over. The spools are constructed of a rubber material to which mud and rot readily adheres. The produce is often damaged because when one spool is rotating down the next is rotating up. If the down rotation spool finds a high friction surface and the up rotation spool has a low friction surface the produce is pinched, broken or squashed through the hole.
A star table is a series of rotating shafts which can be adjustable as to space between the shafts and as to rotational speed. The star is constructed of soft rubber. The produce articles are hit by the rotating stars; the large articles are lifted and the soft dirt is broken; the small articles that miss the flailing of the rubber stars will fall through the opening. The problems are the openings are not round, therefore adjusting the width between the shafts provides only a hit and miss as to how many one can allow to fall through. Accuracies are not possible due to the majority of produce being round in shape rather than square. The separation accuracies are less than 50%, most probable only 25% of undersize will fall through and 75% will carry over. To achieve the levitation needed one must rotate the shafts fast enough for the stars to hit the larger produce hard enough and often enough to allow the smaller size produce to slip through. In the slapping effect, even with the soft rubber stars, a slight disappearance of the skin or net happens each time the produce is struck. The effect on freshly harvested produce, such as potatoes, which are not fully matured, if slapped long and hard enough in the abrasion of dirt and sand, will remove all the skin. If the potato has a low pulp temperature such as in storage, any drop or impact will cause considerable damage, and more so as the pulp temperatures are reduced below 45 degrees F.
An electronic weight sizer or an electronic profile, although accurate, is very expensive and requires an environment not available in the field. The produce to be sized by weight or profile first has to be measured one piece at a time, thus the volumes to be separated are limited. Dirt, rocks and dust would surely damage the electronics.